Imitating a sound with a sound is not a metaphor.
Imitation is based on simulating the sounds of things in the objective world as the basis for word creation.
There are two situations: one is simply simulating the sound of things, mainly describing the sound. The phonetic form of such words is similar to the real sound of things, and they are mainly onomatopoeic words, such as: woo woo (sound of wind), tick (sound of rain), woof (dog barking), gurgling (sound of water flowing), jingle (sound of objects hitting), etc. Interjections are actually imitation sounds, such as "ouch, ah, alas" etc. First, it does not simply simulate and describe sounds, but refers to the things that make such sounds. For example: "cuckoo, cicada, grasshopper, chicken, duck, cat" etc.
Example
The first characteristic of poetry describing music is that it uses sound to imitate sound, and the image can be felt.
Music is an auditory image. It is very difficult for readers to fully understand it. It is not the kind of image that can be seen and touched. It cannot be understood through vision and touch. Feelings, this greatly limits the expressive charm of words. But in "Pipa Xing", the author can find a unique way to imitate sounds with sounds, and the music is as wonderful as possible, the image is palpable, and it is vivid and lively.